I. Field of the Invention
The present invention relates generally to fuels for heat production, such fuels being comprised primarily of the waste materials remaining after steel or pig iron production from iron ore and sludge cake from sewage treatment plants.
II. Description of the Prior Art
The iron-containing waste materials are of a class known as thermit materials. Many thermit materials are well known for use as external heat producers for welding, for incendiary compositions, and for other uses. Burch, in U.S. Pat. No. 2,402,947 describes a Flux Forming Fuel and Process. Jones, in U.S. Pat. No. 3,745,077 describes a Thermit Composition for use as an incendiary. Thermit materials have also been used as a retardant in conjunction with higher temperature reactants. Cox, in U.S. Pat. No. 3,181,937 teaches a device which employs this technique.
The term "thermit" generally refers to a mixture of iron oxides and aluminum which, when heated, reacts at temperatures of about 5000.degree. F. The term "thermit" is also used to refer to a combination of any of several reducing metals with iron oxides. The reducing metal may be aluminum, magnesium, and the like. The following reactions are typical: EQU 8Al+3Fe.sub.3 O.sub.4 .fwdarw.9Fe+4Al.sub.2 O.sub.3 EQU 2Mg+Fe.sub.2 O.sub.3 .fwdarw.2Fe+Mg.sub.2 O.sub.3.
Many variations of this type reaction are known in the art. For example, Rejdak, in U.S. Pat. No. 3,020,610 teaches a variation of the method which is particularly useful for welding aluminum to aluminum. Also, see Rejdak's U.S. Pat. No. 3,033,672 which describes a method for welding copper to steel.
The reactions are exothermic and can react at temperatures in excess of about 6000.degree. F. Interestingly, none of the methods to date have used either the method or the easily obtained materials of Applicant's invention. Heretofore, these reactions have typically employed chemically pure materials. Most applications direct the reaction heat to a localized area or specified material as in the case of welding or incendiary applications. Cost and availability of these relatively expensive materials have to date precluded use of such materials for commercial fuel requirements.
The sewage by-products referred to herein are of a type known as sludge cake, or the like. They are high moisture content solids resulting from sewage treatment. Raw sewage undergoes a series of processes to kill harmful bacteria and place the sewage in a safe, easily disposable form. These processes include skimming, settling, conveying, and others. Heretofore, the sludge cake has been simply disposed of without any benefit thereafter.
It is therefore an object of the present invention to beneficially utilize sludge cake from sewage treatment plants.
It is also an object of the present invention to overcome the cost and availability restrictions of conventional fuels and previously known thermit materials.
These and other objects of the present invention will become apparent to one skilled in the art by an analysis of the following description of the preferred embodiment.